matplotlib · QuLogic · Mar 29, 2022 · Jan 29, 2022 · Jan 29, 2022 · Jan 29, 2022
diff --git a/lib/matplotlib/tests/test_triangulation.py b/lib/matplotlib/tests/test_triangulation.py
@@ -12,6 +12,67 @@
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
 
 
+class TestTriangulationParams:
+    x = [-1, 0, 1, 0]
+    y = [0, -1, 0, 1]
+    triangles = [[0, 1, 2], [0, 2, 3]]
+    mask = [False, True]
+
+    @pytest.mark.parametrize('args, kwargs, expected', [
+        ([x, y], {}, [x, y, None, None]),
+        ([x, y, triangles], {}, [x, y, triangles, None]),
+        ([x, y], dict(triangles=triangles), [x, y, triangles, None]),
+        ([x, y], dict(mask=mask), [x, y, None, mask]),
+        ([x, y, triangles], dict(mask=mask), [x, y, triangles, mask]),
+        ([x, y], dict(triangles=triangles, mask=mask), [x, y, triangles, mask])
+    ])
+    def test_extract_triangulation_params(self, args, kwargs, expected):
+        other_args = [1, 2]
+        other_kwargs = {'a': 3, 'b': '4'}
+        x_, y_, triangles_, mask_, args_, kwargs_ = \
+            mtri.Triangulation._extract_triangulation_params(
+                args + other_args, {**kwargs, **other_kwargs})
+        x, y, triangles, mask = expected
+        assert x_ is x
+        assert y_ is y
+        assert_array_equal(triangles_, triangles)
+        assert mask_ is mask
+        assert args_ == other_args
+        assert kwargs_ == other_kwargs
+
+
+def test_extract_triangulation_positional_mask():
+    # mask cannot be passed positionally
+    mask = [True]
+    args = [[0, 2, 1], [0, 0, 1], [[0, 1, 2]], mask]
+    x_, y_, triangles_, mask_, args_, kwargs_ = \
+        mtri.Triangulation._extract_triangulation_params(args, {})
+    assert mask_ is None
+    assert args_ == [mask]
+    # the positional mask must be caught downstream because this must pass
+    # unknown args through
+
+
+def test_triangulation_init():
+    x = [-1, 0, 1, 0]
+    y = [0, -1, 0, 1]
+    with pytest.raises(ValueError, match="x and y must be equal-length"):
+        mtri.Triangulation(x, [1, 2])
+    with pytest.raises(
+            ValueError,
+            match=r"triangles must be a \(N, 3\) int array, but found shape "
+                  r"\(3,\)"):
+        mtri.Triangulation(x, y, [0, 1, 2])
+    with pytest.raises(
+            ValueError,
+            match=r"triangles must be a \(N, 3\) int array, not 'other'"):
+        mtri.Triangulation(x, y, 'other')
+    with pytest.raises(ValueError, match="found value 99"):
+        mtri.Triangulation(x, y, [[0, 1, 99]])
+    with pytest.raises(ValueError, match="found value -1"):
+        mtri.Triangulation(x, y, [[0, 1, -1]])
+
+
 def test_delaunay():
     # No duplicate points, regular grid.
     nx = 5
@@ -177,6 +238,49 @@ def test_tripcolor():
     plt.title('facecolors')
 
 
+def test_tripcolor_color():
+    x = [-1, 0, 1, 0]
+    y = [0, -1, 0, 1]
+    fig, ax = plt.subplots()
+    with pytest.raises(ValueError, match="Missing color parameter"):
+        ax.tripcolor(x, y)
+    with pytest.raises(ValueError, match="The length of C must match either"):
+        ax.tripcolor(x, y, [1, 2, 3])
+    with pytest.raises(ValueError,
+                       match="length of facecolors must match .* triangles"):
+        ax.tripcolor(x, y, facecolors=[1, 2, 3, 4])
+    with pytest.raises(ValueError,
+                       match="'gouraud' .* at the points.* not at the faces"):
+        ax.tripcolor(x, y, facecolors=[1, 2], shading='gouraud')
+    with pytest.raises(ValueError,
+                       match="'gouraud' .* at the points.* not at the faces"):
+        ax.tripcolor(x, y, [1, 2], shading='gouraud')  # faces
+    with pytest.raises(ValueError,
+                       match=r"pass C positionally or facecolors via keyword"):
+        ax.tripcolor(x, y, C=[1, 2, 3, 4])
+
+    # smoke test for valid color specifications (via C or facecolors)
+    ax.tripcolor(x, y, [1, 2, 3, 4])  # edges
+    ax.tripcolor(x, y, [1, 2, 3, 4], shading='gouraud')  # edges
+    ax.tripcolor(x, y, [1, 2])  # faces
+    ax.tripcolor(x, y, facecolors=[1, 2])  # faces
+
+
+def test_tripcolor_warnings():
+    x = [-1, 0, 1, 0]
+    y = [0, -1, 0, 1]
+    C = [0.4, 0.5]
+    fig, ax = plt.subplots()
+    # additional parameters
+    with pytest.warns(UserWarning, match="Additional positional parameters"):
+        ax.tripcolor(x, y, C, 'unused_positional')
+    # facecolors takes precednced over C
+    with pytest.warns(UserWarning, match="Positional parameter C .*no effect"):
+        ax.tripcolor(x, y, C, facecolors=C)
+    with pytest.warns(UserWarning, match="Positional parameter C .*no effect"):
+        ax.tripcolor(x, y, 'interpreted as C', facecolors=C)
+
+
 def test_no_modify():
     # Test that Triangulation does not modify triangles array passed to it.
     triangles = np.array([[3, 2, 0], [3, 1, 0]], dtype=np.int32)

diff --git a/lib/matplotlib/tri/triangulation.py b/lib/matplotlib/tri/triangulation.py
@@ -1,5 +1,7 @@
 import numpy as np
 
+from matplotlib import _api
+
 
 class Triangulation:
     """
@@ -41,7 +43,9 @@ def __init__(self, x, y, triangles=None, mask=None):
         self.x = np.asarray(x, dtype=np.float64)
         self.y = np.asarray(y, dtype=np.float64)
         if self.x.shape != self.y.shape or self.x.ndim != 1:
-            raise ValueError("x and y must be equal-length 1D arrays")
+            raise ValueError("x and y must be equal-length 1D arrays, but "
+                             f"found shapes {self.x.shape!r} and "
+                             f"{self.y.shape!r}")
 
         self.mask = None
         self._edges = None
@@ -56,13 +60,25 @@ def __init__(self, x, y, triangles=None, mask=None):
         else:
             # Triangulation specified. Copy, since we may correct triangle
             # orientation.
-            self.triangles = np.array(triangles, dtype=np.int32, order='C')
+            try:
+                self.triangles = np.array(triangles, dtype=np.int32, order='C')
+            except ValueError as e:
+                raise ValueError('triangles must be a (N, 3) int array, not '
+                                 f'{triangles!r}') from e
             if self.triangles.ndim != 2 or self.triangles.shape[1] != 3:
-                raise ValueError('triangles must be a (?, 3) array')
+                raise ValueError(
+                    'triangles must be a (N, 3) int array, but found shape '
+                    f'{self.triangles.shape!r}')
             if self.triangles.max() >= len(self.x):
-                raise ValueError('triangles max element is out of bounds')
+                raise ValueError(
+                    'triangles are indices into the points and must be in the '
+                    f'range 0 <= i < {len(self.x)} but found value '
+                    f'{self.triangles.max()}')
             if self.triangles.min() < 0:
-                raise ValueError('triangles min element is out of bounds')
+                raise ValueError(
+                    'triangles are indices into the points and must be in the '
+                    f'range 0 <= i < {len(self.x)} but found value '
+                    f'{self.triangles.min()}')
 
         if mask is not None:
             self.mask = np.asarray(mask, dtype=bool)
@@ -135,35 +151,43 @@ def get_from_args_and_kwargs(*args, **kwargs):
         """
         if isinstance(args[0], Triangulation):
             triangulation, *args = args
+            if 'triangles' in kwargs:
+                _api.warn_external(
+                    "Passing the keyword 'triangles' has no effect when also "
+                    "passing a Triangulation")
+            if 'mask' in kwargs:
+                _api.warn_external(
+                    "Passing the keyword 'mask' has no effect when also "
+                    "passing a Triangulation")
         else:
-            x, y, *args = args
-
-            # Check triangles in kwargs then args.
-            triangles = kwargs.pop('triangles', None)
-            from_args = False
-            if triangles is None and args:
-                triangles = args[0]
-                from_args = True
-
-            if triangles is not None:
-                try:
-                    triangles = np.asarray(triangles, dtype=np.int32)
-                except ValueError:
-                    triangles = None
-
-            if triangles is not None and (triangles.ndim != 2 or
-                                          triangles.shape[1] != 3):
-                triangles = None
-
-            if triangles is not None and from_args:
-                args = args[1:]  # Consumed first item in args.
-
-            # Check for mask in kwargs.
-            mask = kwargs.pop('mask', None)
-
+            x, y, triangles, mask, args, kwargs = \
+                Triangulation._extract_triangulation_params(args, kwargs)
             triangulation = Triangulation(x, y, triangles, mask)
         return triangulation, args, kwargs
 
+    @staticmethod
+    def _extract_triangulation_params(args, kwargs):
+        x, y, *args = args
+        # Check triangles in kwargs then args.
+        triangles = kwargs.pop('triangles', None)
+        from_args = False
+        if triangles is None and args:
+            triangles = args[0]
+            from_args = True
+        if triangles is not None:
+            try:
+                triangles = np.asarray(triangles, dtype=np.int32)
+            except ValueError:
+                triangles = None
+        if triangles is not None and (triangles.ndim != 2 or
+                                      triangles.shape[1] != 3):
+            triangles = None
+        if triangles is not None and from_args:
+            args = args[1:]  # Consumed first item in args.
+        # Check for mask in kwargs.
+        mask = kwargs.pop('mask', None)
+        return x, y, triangles, mask, args, kwargs
+
     def get_trifinder(self):
         """
         Return the default `matplotlib.tri.TriFinder` of this